...
my $parser = new MIME::Parser;
$parser->output_dir("unpacking");
$parser->parse_open("receiving/message-1.msg");
...

##</code><code>##

(.csv)

------_=_NextPart_001_01CF26C0.66530897
Content-Type: application/x-msexcel;
	name="stuff.csv"
Content-Transfer-Encoding: base64
Content-Description: stuff.csv
Content-Disposition: attachment;
	filename="stuff.csv"

YSxiLGMsZCxlDQphLGIsY2MsZGQsZWVlDQphYSxiYmIsY2NjYyxkZGRkZCxlZWVlZWUNCg==

------_=_NextPart_001_01CF26C0.66530897--

##</code><code>##

(.txt)

------_=_NextPart_001_01CF26C0.A0C3FDAB
Content-Type: text/plain;
	name="stuff.txt"
Content-Transfer-Encoding: base64
Content-Description: stuff.txt
Content-Disposition: attachment;
	filename="stuff.txt"

YSxiLGMsZCxlDQphLGIsY2MsZGQsZWVlDQphYSxiYmIsY2NjYyxkZGRkZCxlZWVlZWUNCg==

------_=_NextPart_001_01CF26C0.A0C3FDAB--